Fermented Foods

Fermented foods are known for boosting your immune system, protecting against disease, and aiding digestion, however research has also revealed their ability to help with numerous other health conditions including reducing inflammation, lowering blood pressure, and aiding atherosclerosis and anxiety, to name just a few.

Fermented foods have had a central position throughout history in almost every culture. There are two main methods through which foods are fermented. They can either be fermented through a natural process where the microorganisms  are present naturally in the raw food, for example, in sauerkraut or kimchi, or they can be fermented by the addition of starter cultures, for example with kefir, kombucha and natto.

Fermented foods contain probiotic microorganisms, the ‘good bacteria’, such as lactic acid bacteria which exert a positive physiological effect in the gut by competing with pathogenic bacteria.

Lactic acid bacteria produce bioactive peptides and polyamines which provide beneficial effects on many body systems, including your metabolism and your cardiovascular and immune systems. They’re also involved in converting antioxidant compounds such as flavonoids into their biologically active form.

Fermentation of foods also helps to reduce the toxins and anti-nutrients in the food. For example, the fermentation of soybeans reduces their phytic acid concentrations whilst sourdough fermentation reduces the content of FODMAPs (fermentable short chain carbohydrates) within the bread, allowing it to be better tolerated and more easily digested.

Research is increasingly demonstrating the wide ranging benefits of probiotic foods on all body systems, not just your digestive health.

Sourdough Bread

Sourdough starter culture is produced through the fermentation of flour by lactic acid bacteria and yeasts that originate from the flour and surrounding environment. Unlike standard bread, which is produced through a rapid yeast-only fermentation process, the symbiotic sourdough fermentation of both bacteria and yeast improves bread quality, including texture, flavour, nutritional content and shelf-life, without the need for additives.

During the fermentation process, the bacteria and enzymes convert oligosaccharides and proteins such as gluten into more tolerable forms. Those with gluten sensitivity who are not coeliacs may be able to tolerate sourdough bread more easily than non-sourdough bread.


The lower content of the bread’s non-digestible oligosaccharides, fructans and raffinose (types of FODMAPs), also enable the bread to be better tolerated, especially by patients with IBS and digestive complaints related to FODMAP intolerances. This change in the carbohydrate content occurs due to the degradation of oligosaccharides by the sourdough microorganisms, especially the yeasts Saccharomyces cerevisiae and Kluyveromyces marxianus.

The benefits of modifying the nutritional content of bread through the sourdough process was shown in a randomised control trial of 87 patients with IBS. This study examined the impact of a sourdough rye bread prepared using a specific sourdough system that lowers the FODMAP content of the bread versus a traditionally-made sourdough bread in people with gastrointestinal symptoms.

Results demonstrated a significantly lower breath hydrogen level, and significantly milder flatulence, abdominal cramps, rumbling and other gastrointestinal symptoms following a four week consumption of a low FODMAP sourdough rye bread.

Kefir

Kefir is a fermented milk drink with a creamy texture and sour taste and is produced by adding a starter culture of kefir grains to milk. Kefir grains contain a wide range of microbial species including yeasts, lactic acid and acetic acid producing bacteria.


Kefir has an important impact on the population of microbiota in your gut, with increases in the beneficial bacteria, Lactobacillus, Lactococcus and Bifidobacterium concentrations.


Studies have shown that kefir exhibits antimicrobial activity against pathogens including candida albicans, salmonella pathogens, enterococcus and staphylococcus. Research has also demonstrated their beneficial effects in stimulating the immune system, aiding constipation as well as having potential antioxidant, anti-hypertensive, anti-carcinogenic, cholesterol lowering and glucose lowering effects.

Dairy containing kefir is better tolerated by people with lactose malabsorption since it contains β-galactosidase expressing bacteria such as Kluyveromyces marxianus, which hydrolyses lactose, thus reducing lactose concentrations in the drink. However if it is the milk proteins such as casein to which you are sensitive, rather than the lactose, you may still find kefir dairy difficult to tolerate.

Research has shown that kefir may be beneficial while undergoing antibiotic treatment for H. pylori infections. A double-blind randomised control trial investigated the impact of drinking 500 mL/day kefir, compared to 250 mL/day milk, on Helicobacter pylori eradication rates in patients with dyspepsia and diagnosed H. pylori infection who were taking a triple antibiotic therapy for 2 weeks.


The study found that the rate of H. pylori eradication was significantly higher in those drinking kefir (78%) compared to the control group and the occurrence of diarrhoea, abdominal pain and nausea were also significantly lower. 

Kombucha

Kombucha is a fermented tea beverage reported to have originated in Northeast China in around 220 BC and consumed extensively during the Qin Dynasty. Subsequent to this, fermented tea beverages also became popular in Russia and Eastern Europe. In modern societies, a range of kombucha beverages are available commercially, although the microbial and metabolite composition of these products are not usually listed on the beverage label.

Traditional kombucha is produced through aerobic fermentation of black or green tea and white sugar by the symbiotic culture of bacteria and yeast. The yeast converts sucrose to ethanol (in addition to organic acids and carbon dioxide) which acetic acid bacteria convert to acetaldehyde and acetic acid.

The bacterial and fungal species involved typically include acetic acid bacteria (Acetobacter, Gluconobacter), lactic acid bacteria (Lactobacillus, Lactococcus) and yeasts (Saccharomyces, Zygosaccharomyces)

Antimicrobial actions

The low pH of kombucha, owing mainly to the production of high concentration of acetic acid, has been shown to prevent the growth of pathogenic bacteria such as Helicobacter pylori, Escherichia coli, Salmonella typhimurium and Campylobacter jejuni.

Blood sugar & Cholesterol regulation

In animal studies, kombucha has been shown to exert effects on blood sugars, oxidative stress, diabetes Type-I-induced weight loss, and hypercholesterolaemia.

Increased Antioxidant status

During kombucha fermentation, the concentration of antioxidants such as polyphenols and flavonoids in tea increases along with its free radical scavenging activity.

Sauerkraut

Sauerkraut is one of the most common forms of preserved cabbage and is eaten frequently in Germany, but also in other European and Asian countries as well as the United States. Sauerkraut is produced from a combination of shredded cabbage and 2.3%−3.0% salt, which is left to undergo spontaneous fermentation, generally involving Leuconostoc spp., Lactobacillus spp., and Pediococcus spp.


Sauerkraut (both homemade and shop-bought) has been shown to contain a variety of microorgansims including Bifidobacterium dentium, Enterococcus faecalis, various Lactobacillus species, Staphylococcus epidermidis, Weissella confusa, Lactococcus lactis and Enterobacteriaceae.


Research has demonstrated that sauerkraut can be useful in reducing the severity of IBS symptoms, although the exact mechanisms of this effect remained unclear.

Kimchi

Kimchi, originates from Korea, and consists of a mix of salted and fermented vegetables including Chinese cabbage and/or radishes, and various natural flavouring ingredients (e.g., chilli, pepper, garlic, onion, ginger), seasonings (e.g., salt, soybean sauce, sesame seed), and other additional foods (e.g., carrot, apple, pear, shrimps).


Kimchi is produced by soaking cabbage in salty water and drained, then mixed with the seasonings, spices and food products and then left for the fermentation to take place.

The fermentation occurs spontaneously by the microorganisms naturally found on the cabbage and other foods included in the mixture, although for commercial production of kimchi, starter cultures may also be added.

As kimchi can comprise a variety of ingredients, the microbial composition varies depending on the type and amount of the foods included. For example, a higher Lactobacillus concentration has been found when kimchi contains a higher garlic quantity, while the addition of chilli powder has been shown to result in higher Weissella and lower Leuconostoc and Lactobacillus proportions. Several other microorganisms and yeast species have also been identified in commercially available kimchi.

Since kimchi comprises a variety of ingredients, its impact on your gut microbiota and health is thought to result from a synergistic effect of the microorganisms it contains, as well as the nutrient content (e.g., phytochemicals, fibre, vitamins) of the foods used in the preparation. For example, antimicrobial and antioxidant effects have also been attributed to certain food constituents of kimchi, such as chilli and garlic. Different types and quantities of ingredients in kimchi may also impact your microbiota differently. Animal studies have shown that kimchi may have weight controlling properties, LDL cholesterol reduction abilities, and anti-inflammatory effects.

In vitro studies have also shown that kimchi may exhibit anti-carcinogenic properties and inhibit the growth of gastric cancer cells, however the results of population based research into kimchi’s anti-cancer effects have been mixed. A number of epidemiological studies have shown an increased risk of gastric cancer in the Korean population with higher kimchi intake, which has been suggested to be due to its nitrite, nitrate and salt content.

Yet in contrast to this, a case control study of 136 patients diagnosed with gastric cancer and 136 healthy controls showed that different types and preparations of kimchi were associated with different levels of gastric cancer risk; for example, moderate baiechu kimchi (prepared with salted Chinese cabbage) intakes were associated with a lower gastric cancer risk while moderate intakes of kkakduki (prepared with salted radish) were associated with a higher gastric cancer risk. These differences are most likely due to the different food and nutrient composition and preparation methods of the different types of kimchi.

Natto

Natto is linked to various health benefits due to its vast nutrient profile. Natto is a traditional Japanese food consisting of fermented soybeans with a nutty flavour, sticky and stringy texture and pungent smell. It is often served with cooked rice and seasonings such as green onions, chives, wasabi or pickled ginger. If you want to start adding natto to your diet it can usually be found in your local Japanese supermarket.


As with other fermented soybean foods, natto contains fewer antinutrients and more beneficial plant compounds and enzymes than non-fermented soybeans while its antioxidant, micronutrient and mineral content is increased.


Natto contains the enzyme nattokinase which acts as a blood thinner, improving blood flow and destroying blood clots, thereby reducing the risk of stroke and heart attack. Natto is also high in vitamin K2 which plays an important role in bone health and increasing bone mineral density. Studies in Japan have shown postmenopausal women who had a regular intake of natto were less likely to experience bone loss and were therefore better protected against osteoporosis.

Boost your Health with Fermented Foods

Adding fermented foods into your regular diet is a great way to start reaping the rewards of their beneficial effects, enhance your digestive system, boost your immune system and support your overall health.